30 



But in addition to the positive evidence afforded by the 

 comparison of the analyses of the two soils, that there is no 

 exhaustion of the food of the clover, we have the high 

 authority of Professor Liebig, who says — " In some neigh- 

 " bourhoods clover will not thrive till the sixth year, in others 



not till the twelfth ; flax in the second or third year. All 

 " this depends on the chemical nature of the soil, for it has 

 " been found by experience that in those districts where the 

 " intervals at which the same plants can be cultivated with 

 " advantage are very long, the time cannot he shortened even 



by the use of the most powerful manures. The destruction 

 " of the peculiar excrements of one crop must have taken 

 " place before a new crop can be produced." 



Indeed, Mr. Legard himself almost proves that its failure 

 cannot on the Chalk Wolds be ascribed to the want of any 

 ingredient of the clover, when he says — " That for a period 

 "of 18 years he has used bones to the turnip crops at the 

 "rate of two quarters per acre; to the clovers, rich farm 

 " yard dung, 10 tons per acre ; and to the wheat crops, rape- 

 " dust at the rate of 12 bushels per acre ; and that the clover 

 " crops have been consumed on the ground by sheep." — 

 Surely if land be manured in this way, no exhaustion of the 

 soil can take place. And upon the Magnesian Limestone it is 

 scarcely possible that exhaustion of any specific ingredient 

 can be the cause of failure, because it is the custom to sow 

 beans upon these " clover-sick" lands wherever the soil is 

 not very shallow ; and if a good crop of beans can be grown 

 on the same lands, it follows that certain fixed ingredients 

 must have been present in the soil, for beans contain as much 

 potash, soda, magnesia, alumina, and silica, as red clover, 

 but a little less gypsum, phosphoric acid, and chlorine; but 

 not an absence of the three last, otherwise they would not 

 grow at all. In fine, this single consideration alone, that the 

 clover flourishes luxuriantly during the warm and growing 



